British Airways has an interesting sale running from the U.S. to the U.K. (You may need to be logged into a British Airways Executive Club account to see the page.)
Coach (“World Traveller”) from several cities for less than $400 roundtrip — okay, so far so good, this is frequently available in late October, November, and December (though the price cutting starts early this year).
But perhaps more interestingly, World Traveller Plus — their premium economy product, think something like U.S. domestic first class — is available for about $585 roundtrip. That’s an upgrade that seems worth it to me.
I’d guess the hassles flying in and out of London are affecting BA’s bookings…